Clamp for master sheets of rotary printing machines



New. I9, 1957 L. F. MITCHELL ET AL 2,813,482

CLAMP FoR MASTER SHEETS oF ROTARY PRINTING MACHINES F1166. Dec. 20, 1954 4 SheetsSheet l TR1@ R n i A INVENTORJ.

L fsm? E /7/ 701ML? .D0/VAL o rfwarbe Nov. 19, 1957 L. F. MITCHELL ET AL 2,813,482

CLAMP FOR MASTER SHEETS OF ROTARY PRINTING MACHINES Filed Deo. 20. 1954 4 Sheets-Sheet 2 Nov. 19, 1957 1 F. MITCHELL VET AL 2,813,482

CLAMP FOR MASTER SHEETS 0F ROTARY PRINTING MACHINES Filed Deo. 20, 1954 4 Sheets-Sheet 3 Nov. 19, 1957 1 F. MITCHELL ETAL 2,813,482

CLAMP FOR MASTER SHEETS y01"" ROTARY PRINTING MACHINES Filed Deo. 20, 1954 Don/,4L o 0, Bern/5 TEE HrroeA/ey/ nite `dairies i' atent Ctitice 2,813,482 Patented Nov. 19, 1957 CLAMP FOR MASTER SHEETS F RTARY PRINTING MACHINES Application December 20, 1954, Serial No. 476,472 13 Claims. (Cl. lill- 132) This invention relates to a device for attaching a master sheet to the drum or cylinder of a rotary printing machine, and more particularly to improvements in or relating to mechanisms for securing and releasing one end of a thin exble master printing plate or sheet to the master cylinder of a rotary printing or duplicating machine of the type adapted for oiiice use. These therefore are the general objects of the present invention.

Rotary printing machines of the type adapted for oiice use as duplicating machines, generally use thin flexible master printing plates or sheets from which the required number of copies are made by hectograpbic, lithographie, or any other well known printing process. Such printing plates may be made of metal foils, sheets of treated paper, or the like. Frequently, in ofce use, it is desirable that a small number of copies be made from each of a plurality of master printing plates or sheets. Accordingly, it is desirable in such machines to provide for the rapid replacement of the master sheet. Further, it is frequently desirable to make a number of copies of a portion of the data on a principal printing plate together with the data from a supplemental printing plate, followed by the production of a number of Icopies of all of the data of the principal plate. Accordingly, it is desirable to provide for rapid replacement of a principal and a supplemental printing plate, and for the removal and replacement of the supplemental printing plate Without disturbing the principal plate. These, therefore, are more speciiic objects of the present invention.

This invention contemplates the attainment of its objects by providing a rotary printing cylinder or drum with a plurality of sheet grippers mounted for individual movement to and from sheet gripping or clamping and sheet releasing or receiving positions, together with an operating mechanism which will automatically move certain of the grippers to a sheet releasing or receiving position consequent upon the rotation of the printing cylinder in a nonprinting direction to a predetermined position, and thereafter move other grippers to a sheet releasing or receiving position consequent upon `further rotation of the cylinder in such non-printing position, the grippers being biased toward their clamping or gripping positions, and the operating mechanism being so constructed and arranged that rotary movement of the cylinder in a printing direction will permit the biasing means to return all of the grippers to their sheet clamping or gripping positions, where they are retained as long as the cylinder is not rotated in a non-printing direction.

One embodiment of the invention is illustrated in the accompanying drawing in which:

Fig. l is a front elevation of a portion of a rotary printing machine, illustrating a master drum or cylinder, and embodying the present invention, certain portions being broken away to more clearly illustrate the invention; Fig. 2 is a sectional View as indicated by the lines 2 2 of Fig. l and illustrates the printing drum in end elevation;

Fig.r3 is a sectional view throughthe printing drum as indicated by the lines 3-3 of Fig. l, and illustrates the master sheet clamping members in their gripping positions;

Fig. 4 is a fragmentary sectional View as indicated by the lines 4-4 of Fig. l, the clamping members being in their sheet gripping positions;

Fig. 5 is a view similar to Fig. 2, partially broken away to illustrate the clamping members in their sheet receiving or releasing positions;

Fig. 6 is a view similar to Fig. 5 but illustrating the position of the parts when some of the clamping members are closed and others open;

Fig. 7 is a fragmentary View similar to Fig. 2 illustrating the effect on the clamping mechanism of rotation of the printing drum in a printing direction;

Fig. 8 is an enlarged fragmentary detail of the clamping members in the position shown in Fig. 5, wherein the members of both sets are in their sheet receiving or releasing positions;

Fig. 9 is a View similar to Fig. 8 illustrating the clamping members of both sets in their closed or clamping positions;

Fig. l0 is a View similar to Figs. 8 and 9 illustrating the clamping members of one set closed and those of the other set open;

Fig. ll is a View similar to Figs. 8 to 10 illustrating the clamping members of both sets in their clamping positions, the members of each set gripping a printing plate; and

Fig. l2 is a fragmentary sectional detail, the plane of which is indicated by the lines 12-12 of Fig. 1.

In the drawings, the invention is illustrated as embodied in a printing or duplicating machine having a pair of relatively stationary spaced frame members 10 between which a master printing cylinder or drum 1li is rotatably mounted. The cylinder 11 is illustrated as being secured to a shaft 12 which is journaled in bearings 14 mounted in respective frame members 1li. The machine illustrated is of the offset lithographie type. ln such a machine the master printing plate or sheet A is wrapped about the periphery of the cylinder 1l, supplied with ink repellent and ink by suitable applicators, one 0f which includes a roller indicated in Fig. 2 at 15. The inked image of the printing plate carried by the cylinder 11 is transferred by rolling contact to an offset surface 16 of an offset or transfer cylinder 17. The image is transferred from the transfer cylinder 17 to work sheets in the usual manner. The various cylinders may be power driven by a motor through suitable gears, one of which is indicated at 18 in Fig. 1 as being secured to the cylinder 11. The master cylinder 11 also may be manually rotated by a hand wheel or crank such as indicated in Fig. l at i9. In the embodiment illustrated in the drawings the master cylinder 11 is power driven in a counterclockwise direction to effect the normal printing or duplicating operation. This cylinder, however, may be rotated in a clockwise or non-printing direction by means of the crank 19 whenever so desired by the operator.

The clamping mechanism with which the present invention is particularly concerned is mounted in an axially extending gap or recess 2li formed in the periphery of the cylinder 11. This mechanism includes an elongated channel-like support 21, the web .22 of which is secured to one wall 23 of the gap 2li by bolts 24. The upper flange 25 of the support 21 extends axially of the cylinder and lies a short distance below the periphery thereof, so that it may form an anvil 2S against which the end of a master printing plate or sheet A may be clamped. A plurality of plungers or pins 26 are mounted in spaced openings formed in the ilanges 25 for reciprocation in a direction normal to the ilanges.

A thin disc-like clamping member 34B is secured to the upper end of each plunger or pin 26. These clampingl aa tassaY members lie above the upper flange and are aligned in a row which extends axially of the drum. The clamping members are individually biased toward the anvil 28 by springs 31 which encircle respective pins 26 and are interposed between the upper flange 25 of the supporti and respective split retaining rings 32 mounted in annular recesses formed in the pins 26.

When one end of a thin flexible printing plate A isv positioned between the clamping members or discs 3@ and the anvil 28, with its adjacent edge abutting the pins 26 the force of the springs 31 is suliicient to retain the end of the printing plate A firmly afxed to the cylinder 11. However, such retaining force may be supplemented by the engagement of the plate by a series of relatively small sharp metallic spurs 33 carried by a plate 34 which is: interposed between the support 21 and the gap wall 23.. One such spur 33 extends upward in front of each clamping disc 3i) and lies closely adjacent thereto so that a master sheet or plate A will be forced by the discs 3b into engagement with the spurs.

The opposite or trailing end of the printing platemay be unsecured. However, when an overlay or supplemental plate is to be used. it may be desirable to secure the trailing end of the main plate A to the cylinder indicated in the drawings. This is accomplished by a tensioning device including a bracket Sti secured to a wall of the cylinder 2d opposite the support 21. bracket has a ledge which extends into the gap and is provided with a of circumferentially extending slots 52, across which the trailing end of the printing plate may extend. The printing plate is held against the ledge 51 by a retaining bar 53. This bar carries a series of pointed pins 59 which are positioned above respective slots 52 and either pierce the printing plate or engage suitable openings previously formed in the end thereof.

The ends o-f the bar 53 lie against respective ends of the cylinder 1li, and are each provided with an extension 54 having an elongated slot 55, to receive a pin 56 carried by the adjacent end of the cylinder llll, thus forming a pivotal support for the bar. Suitable springs 57 are interposed between the bar 53 and pins 5S carried by the cylinder. These springs bias the bar 5@ in position against the ledge 51 and to draw the bar inwardly whereby the pins 59, which have been forced through the trailing end of the printing plate, act to draw the plate tightly across the surface of the printing cylinder 11 and retain it tensioned.

When it is desired to release the trailing end of the printing plate, the operator grasps a lip portion 6l) of the bar 53 and draws the bar outward against its springs 57 while rocking it clockwise about its pivot pins 56 to free it from engagement with the printing plate.

The present invention is particularly concerned with the clamping members 36 for the leading end of the printing plate and the mechanism for operating the same. The clamping members 3d, heretofore described, are moved to their sheet receiving or releasing position, shown in Figs. 5 and 8, by a common operating rod or bar 40 which is actuated by a cam 65 consequent upon a predetermined rotary movement of the cylinder 11 by the operator.

As shown in the drawings, the rod 40 extends axially of the cylinder within the gap 20 and underlies the inner ends of the plungers 26. The ends of the rod 4@ are mounted in respective brackets 41 which are pivotally mounted on a shaft 42 rotatably journaled in end plates 43 of the cylinder 11. A pair of arms 36 are secured to the shaft 42 within the gap Ztl and adjacent respective brackets 41.

The arms 36 transmit counterclockwise movement of the shaft 42 to the brackets 41 and retain the brackets in position axially on such shaft. Each bracket 41 has an inturned lip 37 (Fig. 4) which overlies its respective arm 36 and carries an adjusting screw 27 which engages This f 4 such arm to transmit counterclockwise movement of the shaft 42 to the brackets 41.

Each bracket 41 carries a pin 38 which extends freely through an enlarged opening 39 in its respective arm 36, and carries an enlarged washer 34 on its outer end. A plurality of wafers 35, encircle the pin 38 between the washer 34 and the arm 36. At least one of these wafers comprises a spring-like member which exerts an axial pressure on the arm to thereby frictionally clutch the arm and bracket together for movement as a unit about the axis of the shaft 42 and yet permit adjustment of the position of the arm relative to the bracket by the adjusting screw 27.

The cam 65, which controlsl the position of the clamping members 30 by actuation of the shaft 42, is fixed to one of the frame members liti of the printing machine as by bolts 67. This cam is positioned in the path of a pawl 45 pivotally mounted as at 48 on an arm 44 secured to one end of the shaft 42 which extends axially beyond the end of the cylinder 11 which lies adjacent the cam 65. A spring 47 normally holds the pawl 4S against a stop 46 carried by the arm 44.

When the cylinder 11 is rotated in a counterclockwise or printing direction, as indicated by the arrow in Fig. 7, the pawl 45 engages the cam` and is rocked about its pivot. The springs 31 togetherl with springs 68 (Fig. l) retain the clamping members 30, the arms 44 and 36, as well as the brackets 41 in their' plate clamping positions, shown in Figs. 3, 4, 9 and ll.y 4 A.iccordingly, rotation of the cylinder 11 in a printing direction has no effect upon the master sheet clamping mechanisms.

Rotation of the cylinder 11 in a clockwise or nonprinting direction to the position indicated in Fig. 5 moves all of the clamping members 3l) to their open position to release or receive a master sheet. Such rotation, indicated by the arrow in Fig. 5, tends to swing the pawl 45 counterclockwise about its pivot 48, this movement being restrained by the stop pin 46, the result is a counterclockwise movement of the pawl carrying arm 44, the shaft 42, the arms 36, and the brackets 41. This movement of the brackets 41 causes the rod 40, carried thereby, to move the pins 26 axially raising their respective clamping members 30 out of contact with the anvil 25 as indicated in Figs. 5 and 8. In this position a previously clamped sheet is released for removal and the clamping members 30 are in position to receive another master sheet.

To position a master sheet, the cylinder 11 is positioned as above described to open the clamps 30. One end of a master sheet is placed on the anvil surface 28 with the adjacent edge thereof abutting the plungers 26 and the left hand edge engaging a side guide 70, hereinafter to be described more fully. This positions the master both circumferentially and axially relative to the `cylinder 11. The operator holds the sheet in such position and slowly rotates the cylinder to move the rod 40 away from the plungers 26 and permit the springs 31 to draw the clamping members 30 toward the anvil 28 and clamp the sheet positioned therebetween. rlhe latter movement of the cylinder may be in either direction, although the construction is such that it is more convenient to use a counterclockwise or printing movement. In either case the pawl 45 quickly disengages the cam 65 and the parts return to their normal positions. i

The edge guide 7l? is carried by an endmost plunger 26, `and is best shown in Figs. l, 3 and 12. As there shown the clamping member 36e of the endmost plungers 26 each comprise an elongated rectangular member which extends beyond the ends of the support to overlie the corners of the master and retain such corners in position. Rotation of the members 30C is prevented by pins 71 Acarried by the respective members and which extend through guiding openings formed in the upper liange 25 `of the support 21.

The nearest member 30e of Fig. 1V terminates in. an i11- estense wardly extending iiange 72 which carries an L-shaped bracket 73 one leg of which forms an abutment or edge guide for the edge of the master sheet. This bracket is adjustable axially of the drum relative to its supporting member 30a. Any suitable means may be provided for this purpose. For instance,`the bracket may be secured to the member 30e by a pair of screws 74 which threadingly engage the member and pass through elongated slots in the bracket.

The clamping mechanism of the present invention, as heretofore mentioned, is so constructed that a second master printing plate or sheet B may be secured in position on the printing cylinder overlaying a previously posi- -tioned plate A. The construction is such that the overlaying sheet B may be placed in position or removed without disturbing the previously positioned sheet A. Thus a small master sheet B may be positioned overlaying one portion of a larger but previously positioned master sheet A, imprints made from the exposed portions of both sheets, the smaller master sheet B removed and another small sheet B substituted therefor, a second set of imprints made of the exposed portion of these two sheets; the smaller sheet B removed and irnprints made of the larger sheet A only.

The positioning of the overlaying master sheet B without disturbing the previously positioned master sheet A is accomplished by making the plungers `26b which carry alternate clamping members 30h, longer than the plungers 26a of the remaining clamping members 30a, and by providing the cam 65 with two steps or portions 65a and dSb. The cam portion, namely 6511, is so arranged that when the cylinder 11 is moved clockwise until the pawl 45 coacts therewith, the longer plungers 2Gb, carrying the clamps 3017, will be moved to a sheet releasing position and the plungers 26a carrying the clamping members 30a will remain in their active clamping position as shown in Figs. 6 and 10. When the cylinder is rotated somewhat further in a clockwise direction, to the position shown in Figs. and 8, the pawl 45 coacts with the cam portion 65a the plungers 26a carrying the clamping members 30a are also moved to an open position.

To position the first master sheet A, the cylinder is rotated clockwise until the pawl 45 passes the cam portion 65h and engages the portion 65a, inwhich position all clamping members are raised. The master sheet A is then positioned on the anvil 28 beneath all clamping members and the cylinder then rotated to permit the clamping members to engage such master sheet and retain it in position as heretofore described.

Following the positioning of the first master sheet A the cylinder again is rotated in a clockwise or non-printing direction. This time the rotation is stopped when the pawl 45 engages the Cam portion 6517. When the cylinder is stopped in this position the plungers 2Gb carrying the clamping members .30h will be raised to a plane above the positioned clamping members 30a. The end of a second master sheet B is then inserted between the clamping members 30b and the previously positioned sheet A. The end of sheet B thus overlays the end of the sheet A and the clamping members 30a which retains the latter in position, as indicated in Fig. l0. The operator then rotates the cylinder in a counterclock- Wise or printing direction whereupon the pawl 45 moves away from the cam without engaging the cam portion 65a. Accordingly the plate B is secured in position as indicated in Fig. 11 without affecting the position of the plate A.

The master sheet B may be released without disturbing the master sheet A by merely rotating the printing cylinder in a clockwise or non-printing direction until the pawl is engaged by the cam portion 65b. The sheet B then may be removed, and replaced, the cylinder again rotated in a counterclockwise or printing direction causing the new sheet to be clamped in position overlaying sheet A.

It is obvious that if desired the overlayin-g sheet B need have no printing image thereon, but may instead be entirely non-receptive to ink, thus enabling its use as a mask to block out undesired portions of the master sheet A'7 The positions of the cylinder required for engagement of the cam portions 65a and 65b may be indicated by visible markings on the cylinder 11 and frame 10, or by a selective stop for the cylinder 11. However, in the embodiment illustrated the arrangement of these cam portions is such that the reaction of such engagement is readily discernible by the operator when manually rotating the cylinder.

From the foregoing it will be apparent that there is provided a simple and eticient mechanism for clamping master sheets to the drums of printing machines wherein an overlay sheet may be affixed to the cylinder without disturbing a previously positioned sheet and wherein either or both sheets may be inserted or replaced with but little effort and in a relatively short interval of time.

Furthermore, the clamping mechanism is so constructed that it may be applied readily to existing printing or duplicating machines.

While a preferred embodiment of the invention is illustrated and described, it is to be understood that this is capable of variation and modification and therefore it is desired to include such changes, modifications, and alterations as may fall within the purview of the claims.

We claim:

1. A master sheet clamping mechanism for the master cylinder of a rotary printin-g machine having a frame in which the cylinder is rotatably mounted, said cylinder being adapted to support a thin flexible master printing sheet on its periphery with an end of the sheet secured to the cylinder by the clamping mechanism, said clamping mechanism including a pair of sheet grippers mounted in said cylinder for independent movement from a sheet gripping position to a sheet releasing position, a cam on said frame, means mounted on said cylinder and actuatable by contact with said cam consequent upon a partial rotary movement of the cylinder in a nonprinting direction to a predetermined position to move one of said grippers to its plate releasing position, said means being actuatable by contact with said cam consequent upon a further partial rotation of the cylinder in such direction to move the other gripper to a plate releasing position.

2. In a master sheet clamping mechanism according to claim l wherein the clamping mechanism includes a pair of individual plungers on which respective grippers are mounted, one of said plungers being longer than the other plunger, means biasing said grippers to their gripping positions, and wherein said first named means includes a common operating bar movable to sequentially engage said plungers consequent upon sequential partial rotations of the printing cylinder in a non-printing direction.

`3. A master sheet clamping mechanism according to claim 2 wherein said biasing means acts on the grippers individually, and wherein said cam actuated means 1s active to permit the biasing means to restore said grippers to their gripping positions consequent upon a .rotation of the cylinder in a printing direction and maintain them in such gripping positions as long as the drum is rotated in a printing position. a

4. In a sheet clamping mechanism for a rotary printing machine having a rotary printing cylinder adapted to support a sheet on its periphery with an end of the sheet secured `to the cylinder by a cylinder supported clamping mechanism, said mechanism including a pair of sheet grippers mounted for individual movement from a sheet gripping position to a sheet releasing position, means acting automatically to move one of said grippers to its sheet releasing position consequent upon rotary movement of the cylinder in a non-printing direction to a predetermined position, said means being operable to automatically move the other gripper to a sheet releasing position consequent upon further rotation of the cylinder in such direction to a second position, means to bias said `grippers toward sheet gripping positions, and means to render said iirst-named means active to permit said biasing means to restore both grippers to their clamping positions and retain them in such clamping positions consequent upon rotation of the printing cylinder in aA printing direction.

5. In a sheet clamping mechanism for a rotary printing machine having a rotary printing cylinder adapted to support a sheet on its periphery with an end or" the sheet secured to the lcylinder by a cylinder supported clamping mechanism, said mechanism including a pair of sheet grippers mounted for individual movement from a sheet gripping position to a sheet releasing position, means acting automatically to move one of said grippers to its sheet releasing position consequent upon rotary movement of the cylinder in a non-printing direction to a predetermined position, said means being operable to automatically move the other gripper to a sheet releasing position consequent upon further rotation of the cylinder in such direction to a second position, means to bias said grippers toward their sheet gripping positions, and means to render said irst named means active to permit the biasing means to restore said grippers to their gripping positions consequent upon a further partial rotation of the cylinder in a non-printing direction.

6. A master sheet clamping mechanism for a rotary printing machine having a rotary printing cylinder adapted to support a master printing sheet on its periphery with an end of the sheet secured to the cylinder by a cylinder supported clamping mechanism, said clamping mechansim including a series of sheet grippers mountedl for individual movement from a sheet gripping position to a sheet releasing and receiving position, means biasing said grippers to their sheet gripping positions, operating means acting automatically to move all of said grippers to their sheet releasing positions consequent .upon rotary movement of the cylinder in a non-printing direction to a predetermined position, control means connected to said operating means and automatically operative consequent upon movement of the cylinder in a printing direction to permit said biasing means to restore all of said grippers to their gripping positions, said control means including means automatically operative consequent upon subsequent rotation of the cylinder in a non-printing direction to a predetermined position short of the first-named position of the cylinder to move alternate grippers to a sheet releasing and receiving position without disturbing the gripping action of the other grippers and to return r such alternate grippers to their gripping positions consequent upon subsequent rotation of the cylinder in a printing direction.

7. A master sheet clamping mechanism according to claim 6, wherein the cylinder is mounted `on a frame and is provided with an axially extending gap in which the clamping mechanism is mounted, and an anvil is positioned in said gap on which one end of a thin exible printing plate may be positioned, said grippers comprising thin disc-like members overlaying said anvil, a pin secured to each of said members and extending inwardly from the anvil and mounted for reciprocation in said anvil, said biasing means including an individual resilient member associated with each pin, certain of said pins extending inwardly a greater distance than other of said pins, said operating means including a rod-like member underlying the inner ends of said pins, said control means inciuding a two-stop cam iixed to said frame and means carried by the cylinder to engage said cam steps and control the position of said last-mentioned member relative to said pins.

8. A master sheet clamping mechanism according to claim 7 wherein, said last-named means includes a shaft carried by and extending axially of said cylinder and on which an arm element projects generally perpendicularly therefrom and issecured thereto, said rod-like member being carried by said shaft, and means on said arm element to cooperate with said cam.

9. A master sheet clamping mechanism according to claim 8 wherein said rod-like member is pivotally mounted on said shaft by projecting bracket elements, an operating arm secured to said shaft Within said cylinder, and an operating connection between said operating arm and said rod-like member.

10. A master sheet clamping mechanism according to cla-im 9, wherein saidy operating connection includes means to frictionally clutch the operating arm and at least one of said bracket elements together for movement as a unit about the axis of said shaft, and means to positively limit the angular movement of the associated bracket element toward said operating arm.

1l.ln a master sheet clamping device according to claim 10, a master sheet edge guide carried by an endmost clamping member and movable therewith.

12. ln a master sheet clamping device according 4to claim 10, a series of sharpened spurs fixed to the cylinder, one spur extending upwardly above the anvil substantially tangential with the edge of said grippers remote from the cylinder gap.

13. A master sheet clamping mechanism for a rotary printing machine having a frame in which a master printing cylinder having an axially extending gap is rotatably supported, said cylinder being adapted to support a thin exible printing sheet on its periphery with the end of the sheet secured to the cylinder by the clamping mechanism which is mounted in the gap, said clamping mechanism including a plurality of sheet grippers aligned in an axially extending row and mounted for individual movement from a sheet clamping position to a sheet releasing position, means individually biasing said grippers to a gripping position, means active consequent upon rotary movement of the cylinder in a non-printing direction to a predetermined position to move all of said grippers to their sheet releasing and securing position and active consequent upon rotary movement of the cylinder in such direction to a second predetermined position to move alternate grippers to their sheet releasing and receiving positions while retaining the other grippers in their sheet clamping positions, said second-mentioned means being active to permit said resilient means to restore any released gripper to its clamping position and retain it in such position consequent upon rotation of the printing cylinder in a printing direction, and wherein said second-mentioned means includes a shaft journaled in the cylinder and operatively connected with said grippers, an arm secured to said shaft, a pawl pivotally connected to said arm, a stop on said arm to restrict counterclockwise movement of said pawl about its pivotal connection to said arm, resilient means to retain said pawl in contact with said stop, a cam fixed to said frame and having two steps to sequentially be engaged by said pawl consequent upon clockwise movement of said cylinder to rotate said shaft, the second engaged step being adapted to rotate said shaft a greater distance than the rst step and means responsive to the rotational movement of said shaft to move said grippers to their releasing position.

References 'Cited in the le of this patent 

